Process of froth flotation of ores



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PROCESS OF FROTH FLOTATION OF CRES Filed Aug. 22, 1958 17 Sheets-Sheet 17 3,094,484 PRCESS F FROTl-l FLOTATION 0F @RES Alfonso Rino-kanon R., A. de la Torre Gonzales 147, San isidro, Lima, Peru Filed Aug. 22, 1958, Ser. No. 756,680 i Claims. (Cl. 209-166) This invention relates to a metallurgical engineering improvement of the process of froth flotation of ores. It is particularly concerned with new methods for the determination of optimum metallurgical conditions and control of the same in the flotation of ores, that assure maximum practical eiciency during the industrial application of the process.

The invention is further related to the application of said improved methods in the ilotation of oxidized ores amenable to treatment by means of a fatty acid or soap collector and an alkaline modier.

It is furthermore speciiically concerned with a practical application of flotation to the concentration of refractory oxidized lead ores with non-calcareous gangue, employing a silicated-soap reagent, prepared for, and used in the case of each individual ore, according to the mentioned new practical methods that control the maintenance of maximum flotation emciency in the plant operation.

As is well known the llotat-ion treatment of every ore requires the previous ydetermiantion in the laboratory, by means of preliminary tests on a small scale, of the best conditions to carry out the process in practice, which involves choosing the most suitable reagents `for the particular ore being treated, and proportioning the same properly. However, this is something much easier said 'than done as every ore needs special conditions for optimum results that are peculiar to its chemical and mineralogical composition; and every reagent must be specially proportioned in each case, to work at its best, not only in relation to its concentration in the solution of the pulp, and to the ore treated, but also in relation to other reagents used simultaneously. The chemical engineers dream of designing `generic flotation reagents capable of carrying out perfectly and under standard conditions the dilerential ilotation of individual minerals of any ore in the presence of the complex associations `and circumstances found in practice, has not materialized yet, and seems likely to remain a fond hope. Consequently, the laboratory testing work for each ore continues to be unavoidable.

The customary attempt to `determine experimentally the optimum quantity of reagents has been a matter of cut and try. It has been considered an art, not a science. Experience and interest in ones work have counted heavily in this field.

This invention is particularly concerned with methods that will help make dotation testing work a more technically evaluated and precise undertaking and the ilotation process in general more of a metallurgical engineering operation than an art, `design of mechanical apparatus and/or prescription of formulas for chemical reagents, which by themselves cannot possibly assure the best metallurgical and economic solution for every type of ore, and yet have constituted almost all of the work done on the improvements of the previous art.

lt has always been a difficult problem in metallurgical practice to determine the best among a series of experimental tests, or dierent operations; or the best compromise of several solutions, some better from the point of view of concentrate grade, and others with regard to recovery. The ditliculty has stem-med principally from the lack of a just criterion, scientic and realistic at the same time, to measure the eiliciency of a concentrating ite States arent O operation, simultaneously from the two above-mentioned points of view. Under these circumstances it has been practically impossible to deiine accurately the best metallurgical conditions during the laboratory testing work, that would permit optimum results in the practice of iloltation technology. The main problems involved in' the laboratory testing work have been related to the optimum proportioning of reagents, and the control of other variables for the obtention of maximum results, consistent and industrially reproducible.

Furthermore, even supposing that fthe ideal metallurgical conditions for a given treatment have already been determined in the laboratory, it has always been more or less uncertain during the industrial operation of a plant, whether or not these ideal conditions were being reproduced in' practice with their maximum efficiency. It often happens in liotation plants that the addition of many reagents is effected in an individual form, and generally the control of the multiple variables of the process is made separately for each one of them. Hence the joint eiiects can be evaluated only approximately, usually in an uncertain vand defective way, precisely because of the lack of a realistic and scientific criterion with which to measure the metallurgical efficiency obtained. This situation has made it impossible to assure in any case that a 'given plant is operating with its best possible eiciency, even for the reagents combination that it is using, and for the machinery installed.

Lt is thus imperative in' order to increase the efficiency of the flotation process in 4general not only to be able to assess properly the results of testing work or industrial operations, but .also to evolve practical methods for maintaining the best predetermined conditions in the plant.

The present invention consists precisely of a series of integrated practical methods and physical steps based on and made possible by ta new realistic assessment of the eliciency of a otation operation, and designed with the object of teaching the men skilled in the practice of tlotation technology how to determine practically the optimum conditions, metallurgical and economical, for the treatment of any ore, using any type or combination of reagents and flotation machinery; and subsequently how to apply said conditions on an industrial scale with their maximum eiliciency; and :how to control their constant maintenance in the operation of notation plants. Consequently the methods of this invention constitute a new practical process, which compries a series of coordinated steps, starting in the laboratory and ending with the production of re-cleaned concentrates in the flotation plant.

More specifically, a basis of the present invention has been the finding of simple formulas, derived from a logical definition of metallurgical objectives, that can be expressed in terms of the assays of the ore treated and of the products obtained in the flotation operation, and that measure for the first time with only one figure, expressed as percentage of the theoretically possible maximum etilciency, and by an index number that is also a function of time, in a scientic, just and realistic manner, the eiciency of a separation of the valuable elements from the ygarrigue contained initially in the treated ore. These formulas take into account simultaneously the points of v-iew of recovery, grade of the concentrate, ratio of concentration, nature of the ore treated and also the speed of the operation (flotation time).

The invention comprises also new methods to optimize the dotation process that are related to the practical achievement of its very objective of separating in the most eicient possible Way, as dened by the above mentioned formulas, the valuable minerals from the gangue present in the ore treated during the actual plant operation.

The methods involved make use of chemical reagents, mechanical equipment, the new basic mathematical formulas discovered, chemical analyses, pH measuring and controlling electronic devices and specific process flow sheets as mere tools to Iachieve the intended ends of new, useful Iand improved results of the industrial flotation process.

The true metallurgical ellciency as herein disclosed is 'an adequate -system of measurement for the degree 0f 'success achieved in a concentrating operation, whose objective is delined as vthe separation of the valuable mineral from the gangue (or of two groups of minerals or elements), initially contained in the ore treated. It is delined simply by the dilference of the recoveries of the valuable mineral 'and of the -gangue (or of two groups of minerals or elements) in the concentrate obtained in any concentrating operation.

The new kinetic concept of differential oatability which is Ia specific measure of llotation efliciency, takes into Vaccount the speed of the operation, and -as herein disclosed, is defined as the difference of the mean speciiic flotation rates of lthe valuable miner-al and of the -gangue (or of two -groups of minerals or elements) during the total not-ation time interval; and it is given by the ratio of the metallurgical eficiency to the said llotation time. Its physical `dimension is thus reciprocal time, and it is expressed in terms of percent over time.

The mathematical expressions of the formula-s defining the above concepts in function of the products involved, Iassays of the same and of the ore treated, Weight of the concentrate obtained, values of the heads and of the said involved products, and the flotation time, are -as follows:

(A)`B*asic formulas:

(C) In the plant, for the continuous process:

lif Em=Metallurgical eliiciency (percent).

RmF=Recovery of the valuable mineral-s in the froth concentrate F (lloat) (percent).

RgF=Recovery of the gangue in the froth concentrate F (percent).

w=R=atio of froth concentrate weight to weight of heads (weight of concentrated-Weight of tailings).

f=Grade (valuable element content) of the froth concentrate.

h=Grade (valu-able element content) of the heads, or calculated grade of heads as expressed in terms of the weights `and lassays of the products, froth concentrate and tailings, of the batch tests.

m=Grade of the pure numerals being floated (weighted average Iassay of the pure minerals of the valuable element contained in the ore treated, that `are being floated).

s=Grade (valuable element content) of the tailings.

K=Ratio of concentration.

As =Differential floatability (percent/time).

Qmoverau=Mean specilic flotation rate of the valuable mineral, for the total flotation time interval (reciprocal time).

Qgoverau=Mean specific dotation rate of the gangue, lfor the dotation time interv-al (reciprocal time).

I=Total dotation time interval of each laboratory rougher llotation batch test.

Ad E=Dilerential tloatability (percent monetary units per unit time) lbetween all the valuable elements `and the ygangue, bulk or economic differential floatability.

2Vf=Snm of the values of the valuable elements contained in the rougher froth concentrate per ton of concentrate (monetary units).

2Vh=Sum of the values of the valuable elements contained per ton of heads (monetary units).

Zl/mzSum of the values of the valuable elements contained in one ton of the theoretically pure concentrate of the minerals of the valuable elements that are concentrated, present in the ore treated (monetary units).

te='Average time required for the production of a quantity of concentrate with the value of one monetary unit by each laboratory rougher liotation batch test, during the respective total flotation time interval (t).

l/ e=Reciprocal of said time, or production rate in terms of monetary units per unit time (economic capacity).

F :Weight of froth concentrate produced by the laboratory rougher otation batch tests.

PA I =Plant dilferential oatability (in percent tons per hour).

S=Grade of the nal tailings (assay of the valuable element contained in the lin-al trailing).

fc=Grade of the 'final cleaned froth concentrate obtained in the process (assay of the valuable element contained in the final cleaned froth concentrate).

T :Time required for the production of one ton of iinal cleaned lfroth concentrate in the plant (in `a fraction of 1an hour).

l/ TzReciprocal of said time or production rate in tons of concentrate per hour (production capacity of plant). PA t E=Plant differential tloatability of all the valuable `elements (percent monetary units per hour), economic diierential floatability in the plant.

1=Grade of the heads (assay of one of the valuable elements contained in the ore treated).

SzGrade of the final tailings (assay of the same valu- 'able element contained in the final tailing).

f'c=Grade of the lin-al cleaned froth concentrate obtained in the process (assay of the same valuable element contained in the inal cleaned froth concentrate),

EVfC=Sum of the values of the valuable elements contained in the nal cleaned froth concentrate, per ton of concentrate (monetary units).

1/ Tezkeciprocal of the time required for the production of va quantity of final cleaned froth concentrate with the value of one -monetary unit in the plant (in a fraction of an hour), which is `equivalent to the economic production rate of the plant.

As anyone familiar with flotation testing Work will have noticed empirically the best conditions are `generally associated With rapid floatability of the desired minerals. Consequently, when time is taken into consideration together with the metallurgical eciency, that is to say, when the differential floatability :as previously defined and measured, is taken as the criterion to assess flot-ation results, fa complete evaluation of the true llotation ehiciency is obtained, which sharpens dramatically the rdifferences among the various relative results corresponding to different metallurgical conditions, permitting `for the first time a precise determination of the best values of the controllable variables of the process.

The new formulas 'herein disclosed, permit for the rst time the unequivocal determination of the best metallurgical conditions needed to produce optimum results in the practice of flotation technology, in function of the controllable variables of the process.

The values that could be determined as best for the controllable variables of the process through the evaluation of flotation results according to other yardsticks, previously available to the industry, such as the criteria of recovery, grade of concentrate, Gaudins selectivity index, and, even the true metallurgical efficiency as herein disclosed, do not correspond ex-actly to the maximum values obtained by the differential floatability formulas. Consequently if as herewith sustained the latter give the only true assessment of the flotation process efciency it follows that before the disclosures of the present invention it was materially impossible to determine accurately the optimum values of the controllable variables of the process in order to obtain the best possible results of the industrial operation.

The new formulas make it possible as a consequence of the true determination of optimum conditions, to evolve methods `for an adequate technical control to insure their industrial scale application in flotation plants. Finally they permit a proper evaluation of the actual metallurgical results obtained in an industrial operation, in which way Vit is possible to compare said actual results with the optimum results obtainable, thus enabling management to have a close control of operational efficiency.

Thus the roughing oper-ation should have as its true aim to Iachieve maximum differential floatability (maximum metallurgical efficiency in the minimum flotation time) and not simply to achieve a rough recovery of the bulk of the valuable minerals or -a rough rejection of the bulk of the waste. Nothing is gained with 'a 100% recovery of the valuable mineral if simultaneously 'a 100% recovery of the gangue is effected; or with la 100% rejection of the gangnie if simultaneously a 100% rejection of the valu-able mineral is effected. In both these cases the flotation eliiciency is zero, and yet the prior definition of roughing aims was vague enough to include both these `extreme `absurd possibilities.

Consequently the traditional practical expression of flotation operators that the rougher flotation should be worked for recovery and the cleaner flotation should be worked for grade is clearly incorrect. The roughing and cleaning operations of a flotation plant are not different processes with contradictory objectives, but rather two stages of the same process with the same objective. They should supplement each other, with the cleaning operation refining the results obtained in the roughing operations, and not un-doing them. Unfortunately the l-atter case was possible often enough with the previous vague understanding of the true aims of both operations.

Another basic nding of the present invention is that if the maximum differential floatability conditions are establshed in the plant Ifor the rougher operation, they will give place automatically to the greatest differential lloatability conditions during the subsequent cleaning operations, which will accentuate therein, usually without the need of further reagent additions, the superiority of the rougher results, -With respect to the results obtainable under other possible conditions, and thus lassure the optimum economic land metallurgical final results for the complete process.

Therefore the rougher-scavenger operation should not be prolonged more than is absolutely necessary to produce results of maximum differential floatability. The metallurgical conditions necessary to achieve this purpose can be determined practically lby the relative results of batch laboratory rougher flotation tests performed with different amounts of reagents and under different conditions of the controllable variables.

The right iiotation time will thus be a consequence of the use of proper reagent additions, under the correct conditions to produce maximum rougher flotation efficiency.

The metallurgical conditions determined for laboratory rougher batch tests correspond to the -initial conditions in ysaid tests. Said initial conditions in the laboratory tests correspond in turn to the steady-state conditions prevailing `at the beginning of the rougher otation circuit of the plant, and can thus be controlled best at the conditioning stage.

The continuous liotation operation in the plant can he correlated to the operation of a single batch cell in the laboratory better than to fthe operation of a steady-state laboratory flotation cell. The approximation olf test data obtainable from the ordinary laboratory batch cells is sufciently accurate for all practical purposes notwithstanding the dilution necessary to counteract the shrinkage of pulp volume during the course of each laboratory batch test. Consequently this method of laboratory testing work has been proven most practicable for the `objectives of the present invention.

The `operation of a laboratory steady-state iiotation cell may reproduce faithfully perhaps the operation of a single rougher cell of a plant. But Ithe operation of a single laboratory batch rougher `flotation cell reproduces more faithfully the operation of the total rougher string of cells inthe plant, since the operation of the rst rougher cell of the plant can be correlated with the initial moment of the operation of the laboratory batch rougher cell, and the operation of the last scavenger cell of the plant ycircuit can be correlated to the last moments of the operation of the laboratory cell. And of course a similar reasoning `applies to the intermediate cells of the string of plant cells, and to the intermediate moments between initial and nal conditions `of the operation of the laboratory batch cell.

Hence in the present invention the steady-state initial conditions corresponding to the maximum flotation eiciency determined in the laboratory with the rougher batch flotation tests, must be maintained in the conditioning stage at the plant. It is sustained here that the rest of the plant operation will give place to total conditions of maximum efliciency as an inevitable consequence if this prerequisite is assured, which greatly facilitates the plant operational control.

The yoptimum proportioning in the vfeeding of reagents, for the best treatment of any ore, as well as the correct determination of the other controllable variables of the process, become thus Ia real possibility for the first time through the above-defined metallurgical objectives.

The methods disclosed herein evolved from. a practical application of this possibility to the treatment of refractory `oxidized lead ores.

The novelty in its broad aspect of the methods embodying the present invention resides:

(a) In the invention or new formulas which define for the rst time unequivocally the values of the controllable variables of the process, namely, the grinding neness, 

1. THE METHOD TO OPTIMIZE THE PROCESS OF FROTH FLOTATION OF ORES, WHICH COMPRISES PRE-DETERMINING BY A SERIES OF LABORATORY ROUGHER FLOTATION BATH TESTS ON THE ORES, THE VALUES OF THE CONTROLLABLE VARIABLES VIZ, FINENESS OF GRINED, PULP DENSITY, CHEMICAL COLLECTORM FROTHER AND MODIFIER REAGENTS, CONDITIONING TIME AND THE PH RESULTING FROM SAID VARIABLES THAT PRODUCE CONDITIONS OF MAXIMUM DIFFERENTIAL FLOATABILITY, AS DEFINED BY THE ALGEBRAIC DIFFERENCE OF THE MEAN RATES OF RECOVERIES OF THE VALUABLE MINERALS AND OF THE GANGUE IN THE FORTH CONCENTRATE DURING THE TOTAL FLOATION TIME INTERVAL OF THE BATCH TESTS; VARYING THE PROPORTIONS OF TWO CHEMICAL REAGENTS IN EACH SERIES OF TESTE FOR VARIOUS GRINDING FINENESSES AND FOR EACH OF VSRIOUS FIXED COMBUNATIONS OF OTHER REGENTS, PUPL DENSITIES AND CONDITIONING TIMES OF THE GROUND ORES; MEANS URING THE RESULTING PH CORRESPONDING TO EACH BATCH TEST OF EVERY SERIES; EXPRESSING THE CONDITIONS OF THE BATCH TESTS AS FUNCTIONS OF THE PAIR OF CHEMICAL REAGENTS VARIED, AS MEASURED ALONG THE COORDINATE AXES OF A CARTESIAN SYSTEM; NOTING AT THE PLOTTED POINTS THE DIFFERENTIAL FLOATABILITY OF EACH TEST, DRAWING CURVES OF EQUAL DIFFERENTIAL FLOATABILITY FOR THE EXPWRIMENTAL RESULTS OF EACH SERIES OF TESTS, THE ZERO CURVES REPRESENTING CONDITIONS OF NO SEPARATION OF THE VALUABLE MINERALS FROM THE GANGUE, POSITIVES CURVES REPRESENTING CONDITIONS OF CONCENTRATION OF THE VALUABLE MINERALS IN THE FORTH, AND NEGATIVE CURVES REPRESENTING CONDITIONS OF CONCENTRATION OF THE GANGUE IN THE FORTH; TAKING FROM SAID EQUAL-DIFFERENTIAL FLOATABILITY CURVES THE BEST RELATIVE PROPORTION INDICATED BY THE RESPECTIVE COORDIANTES OF THE PAIR OF CHEMICAL REAGENTS WHICH PRODUCES THE GREATEST ABSOLUTE VALUE, POSITIVE OR NEGATIVE, FOR THE DIFFERENTIAL FLOATABILITY IN EACH SERIES OF TESTS, DEFINING THUS THE CONDITIONS CORRESPONDING TO THE MAXIMUM DIFFERENTIAL FLOATABILITY OF ALL THE SERIES OF TESTS, FOR THE TREATMENT OF ANY ORE IN TERMS OF THE CONTROLLABLE VARIABLES OF THE PROCESS, AND THEIR RESULTANT PH. 